Printheads for inkjet printers are precisely manufactured so that the components cooperate with an integral ink reservoir to achieve a desired print quality. However, the printheads containing the ink reservoir are disposed of when the ink supply in the reservoir is exhausted. Accordingly, despite the required precision, the components of the assembly need to be relatively inexpensive, so that the total per page printing cost, into which the life of the assembly is factored, can be kept competitive in the marketplace with other forms of printing.
Typically the ink, and the materials used to fabricate the reservoir and the printhead, are not the greatest portion of the cost of manufacturing the assembly. Rather, it is the labor intensive steps of fabricating the printhead components themselves. Thus, efforts which lower the cost of producing the printhead have the greatest effect on the per page printing cost of the inkjet printer in which the printhead assembly is used.
One way to lower the cost of producing the printhead is to use manufacturing techniques which are highly automated. This saves the expense of paying highly skilled technicians to manually perform each of the manufacturing steps. Another important method for reducing costs is to improve the overall yield of the automated manufacturing process. Using a higher percentage of the printheads produced reduces the price per printhead by spreading out the cost of manufacture over a greater number of sellable pieces. Since process yields tend to increase as the number of process steps required to manufacture a part decrease, it is beneficial to reduce the number of process steps required to manufacture the printhead, or replace complex, low yield process steps with simpler, higher yield process steps.
Thermal inkjet printheads typically contain three and often less than about five major components, (1) a substrate containing resistance elements to energize a component in the ink, (2) an integrated flow features/nozzle layer or nozzle plate to direct the motion of the energized ink and (3) a flow channel layer for flow of the ink to the resistance elements. The individual features which must cooperate during the printing step are contained in the two major components, which are joined together before use.
Nozzle plates for inkjet printheads are formed out of a film of polymeric material that is provided on a reel. The nozzle plates are semicontinuously processed as film is unrolled from the reel. An important part of the process is the removal of individual nozzle plates from the film so that the plates may be attached to a semi-conductor chip surface for installation in the inkjet printhead. It is important that the removal process be conducted in a cost effective manner and that the quality of the resulting printhead structure be sufficient to achieve quality printed images.
In the past, an excimer laser was used to ablate the flow features and nozzle holes in a polymeric material to form nozzle plates and mechanical processes were used to cut the nozzle plates from the polymeric film. Mechanical punching is relatively inexpensive but is incapable of creating additional features on the nozzle plate that may be required for improving the adhesion between the nozzle plate and the semiconductor substrate to which it is attached. Mechanical punching also generates a significant quantity of debris which may interfere with the operation of the nozzle plate. It is also known that mechanical punches wear excessively at the corners and thus cannot achieve tight tolerances for any reasonable length of time, resulting in a high maintenance situation and a loss of product quality over time.
Typically, an adhesive is used to join the nozzle plates removed from the film to the printhead to provide a unitary structure. If the adhesive is applied to one of the nozzle plates or printheads before the manufacturing steps for that component are completed, then the adhesive layer may retain debris created during the various manufacturing steps. Often the debris is difficult to remove, and at the very least requires extra processing steps to remove, thus increasing the cost of the printhead. Additionally, if the debris is not completely removed the adhesive bond between the substrate and the nozzle layer will be impaired resulting in a printhead that either functions improperly or does not exhibit the expected utility lifetime.
If the adhesive is applied to one of the components after the features are formed in that component, additional labor intensive steps are required to ensure that the adhesive is positioned on the portions of the component that are to be used as bonding surfaces, and that the adhesive is removed from those portions of the component whose function will be inhibited by the presence of the adhesive. Not only do these extra steps add to the cost of the printhead, but any error in positioning the adhesive on the components will tend to reduce the yield of product from the printhead manufacturing process.
For example, if adhesive is left in a portion of the component such as a flow channel for the ink, then the proper function of that flow channel will be inhibited, and the printhead will be unusable. Alternately, if the adhesive does not adequately cover the bonding surfaces between the components, then the components may separate, allowing ink to leak from the completed assembly. Both of these conditions will lower the product yield, thereby increasing the cost of the printheads produced, as explained above.
It is an object of this invention, therefore, to provide a method for manufacturing an inkjet printhead that is highly automated.
It is another object of this invention to provide an inkjet manufacturing method that does not require additional process steps for the alignment and removal of adhesive.
It is a further object of this invention to provide a method for manufacturing an inkjet printhead in which the adhesive used to join the components does not attract and retain debris through subsequent process steps.
Another object of this invention is to provide a method for removing nozzle plates from a polymeric film.
A further object of the present invention is to provide a method of attaching a polymeric nozzle plate to a printhead.